Fixed-Time Containment Control of Voltage and Frequency of Microgrids with Grid-Forming and Grid-Following Converters

As a growing portion of inverters in alternating current (AC) micorgrids (MGs) are utilizing the grid-forming (GFM) control due to its superior active grid support capabilities, the hybrid operation of GFM and grid-following (GFL) converters becomes an imperative scenario, making it more complex to achieve coordination among heterogeneous inverters for grid support. This paper investigates the synergetic operation of GFM and GFL inverters for the support of grid frequency and bus voltages. To address the contradiction between the frequency control and voltage regulation missions, the general roles of GFM and GFL are assigned based on a local node‘s power balance profile. Moreover, to simplify the control system design and achieve unified regulation of two indices, a fixed-time containment control (FTCC) scheme is proposed, which chooses two leader distributed generators (DGs) to form a convex hull shaped by the set points of the control objectives and leads the follower DGs for power sharing. In addition, the fixed-time convergence of the control approach is ensured for accelerating the response speed. Hardware-in-the-loop (HIL) experiments are performed to evaluate the feasibility and performance of the proposed method. The experimental results fully validate the effectiveness and superiority in frequency/voltage regulations and robustness performance.